Process for precipitating copper-ammonia solutions of cellulose for the purpose of manufacturing artificial-silk threads or similar products.



-pose UNITED STATES PATENT oFricE.

E ILE GEORGES LEGRA'N'D, or STE. AnaEssE, salmon.

rnocnss FOR rnncrrrrn'rrue COPPER-AMMONIA somr'rrons or eELLuLosE FORTHE V runrosr. or manursc'ruzame ARTIFICIAL-$113K rnnnims on SIMILARraonuer's.

No Drawing.

To all whom it may concern.

Be it known that I, EMILE GEORGES LE- GRAND, a citizen of the Republicof France,

and resident of Ste. Adresse, France, have invented new and usefulImprovements in Processes for Precipitating Oopper-Ammonia SolutionsofCellulose for the Purof Manufacturing Artificial-Silk Threads orSimilar Products, which improvements are fully set forth in thefollowing specification. v

The use of caustic alkalis as coagulatin agents for cupro-ammoniumsolutions of ce .lulose is well known.

In prior processes it has been customary to subject solutions ofcellulose to the action of concentrated soda lyes, thereby preclpltatingthreads of cupro-cellulose, which latter are caused to pass underpressure through suitable capillary orifices. The products obtainedafter neutralizing and washing, are supple and transparent. Theirstrength and elasticity are greater than those of products prepared byprecipitatlon withacidsl Nevertheless, this process has in practiceimportant disadvantages. During the spinning, the bath graduallyacquires a blue color owing to the presence of copper salts in solution.After'a little time, it becomes so colored that it is diflicult to seeand to tie together the broken threads. At the first washing, the upperlayers of thread, in direct contact with water, gradually become whiterand the bottom layers remain dark blue. This results in greatirregularity in the quality of the fibers. The whitish portions producea dull and opaque thread, certain strands remaining shiny andcrystalline, while others have an opalescent milky appearance. Theseirregularities reappear in the dyeing; the thread is spotted, and ontesting there are also found differences in the strength and elasticity.

This invention relates to the addition, to the alkalis, of diastasesolutions capable of decoloring the caustic soda solution by reducingcopper salts in solution, and of reinforcing or strengthening thecellulose fiber by completing the coagulation obtained by means of thealkaline lyes. Such a solution added in proportions of 4% to thespinning bath, produces very important new technical efl'ects.

1. In the presence of hot concentrated caustic soda solution preferablybetween 40 Specification of Letters ma and 45 C. (the reaction is stillpossible from 45-50 (1), the diastase acts as an I Patented Mar. 9,1915. Application filed August-29, 19-12. Serial-No. 717,677.

sugar, etc.) which act only at the tempera- I tures of 45-75 C., thediastase in alkaline medium does not'act above 70 C. From 5070 0. itsreducing and coagulating property gradually decreases. At 75 C. thediastase is completely decomposed. It is therefore necessary that thetemperature of coagulation should not exceed 50 0. Beginning with 40 0.,the copper salts in solution are precipitated, the caustic soda solutionassumes gradually a reddish color, enabling the blue threads to beeasily guided and tied together in the precipitating bath. The copperoXid settles at the bottom of the vats; it is withdrawn by decanting andrecovered in the state of precipitated copper. I 2. The spools chargedwith cupro-cellulose precipitated by the mixture of caustic soda anddiastase in solution, have uniformly the same appearance. The thread, oncoming out from spinning, has a dark green color which it retains evenafter a long washing with water. As soon as it has been deprived ofcopper, it keeps all its transparency and has a bright color. Thestrands do not contain either dull or spotted portions, the dyeing isvery regular and especially brilliant.

3. By the addition of diastase to caustic lyes, the coagulating actionof the precipitating bath is strengthened and lengthened,

.silk. Its strength and elasticity considerably increased by thisprocess, enable it to finda ready market, more particularly inmechanic'al embroidery and weaving.

According to the process forming the subject of this invention, the sameresults can 1O the caustic soda in question be used alone or .beobtained by the simultaneous use of diastase and of diluted alkalinelyes. It is 'pref-' 'erable to use as a precipitating bath weak causticsoda containing 16-21% N aOH with the addition of 3, 4 or 5% diastase,

Up to now, in all processes relating to the precipitation ofcupro-ammonium solutions of cellulose by caustic alkalis, it isspecifiedthat the coagulating liquids are concentrated caustic soda solution orpotash lyes, whether mixed with caustic soda salts or contain anaddition of poly-saccharids and aldehyde alcohols, formaldehyde,glycerin, glucose,

saccharose, lactose, sucrate of lime, etc.

Claims:

' 1. The improvement in processes of the kind described which consistsin subjecting purpose described.

-In testimony whereof I have signed this specification in the presence'of two sub- 30 scribing witnesses. EMILE GEORGES LEGRAND. [1,. 8,]

Witnesses:

G. HOADLEY, CONSTANT GUIERARD.

